• Energy Research
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In response to the intensification of eco-friendly routes as a strategy to access compounds of interest, extraction based on hydrothermal technologies is an efficient method to obtain high yields of compounds present in lignocellulosic materials. Accordingly, this study investigated the effects of the combination of ultrasonic pretreatments (energy density, 1.23 × 103-37.6 × 103 J/cm3; reaction time, 15 and 60 min) and subcritical water hydrolysis (SWH) (temperature, 220°C; flow rate, 10-30 mL/min; and reaction time, 0.5-15 min) on sugar yield profile from residual biomass of rice, soybean, and pecan. A characterization of the sugars present in the hydrolyzed solutions by high-performance liquid chromatography (HPLC) and a physicochemical evaluation of biomasses by Fourier-transform infrared spectroscopy (FT-IR) was performed. The highest yield reported were 23.8/100 g biomass, 14.4/100 g biomass, and 6.0/100 g biomass for pecan shell, rice shell, and soybean straw, respectively. Cellobiose, glucose, xylose, and arabinose were quantified by the HPLC, as well as inhibitors and organic acids. FT-IR indicated the compositions of the fresh and pretreated samples. Appropriately, the combined application of ultrasonic and SWH methods supported the valorization and optimization of high potential materials generated in agricultural processing.

Considerando a importância do conhecimento das paisagens, a possibilidade que ele abre para uso de forma racional dos recursos naturais, o estudo teve como objetivos identificar as características geoambientais, delimitar e mapear as unidades ambientais do município de Juazeiro do Piauí, bem como avaliar as potencialidades e limitações em cada uma das unidades mapeadas. O município estudado localiza-se no Território de Desenvolvimento dos Carnaubais, nordeste do estado do Piauí. A metodologia utilizada no trabalho empregou a abordagem integrada associada a técnicas de campo, laboratório e cartografia digital, fato que possibilitou a efetuação o mapeamento das unidades ambientais, considerando os aspectos topo-morfológicos. Desse modo, foram mapeadas as seguintes unidades geoambientais: Superfície Pedimentada Dissecada em Morros/Colinas e Formas Tabulares de Juazeiro do Piauí, Patamares Estruturais da Bacia do rio Poti e o Vale da Bacia do rio Poti. Ressalta-se que as referidas unidades apresentam potencialidades e limitações distintas para fins de exploração racional dos recursos naturais, dentre as potencialidades pode-se destacar as extensas áreas planas a suave onduladas, solos desenvolvidos (Latossolos), baixa severidade climáticas em alguns trechos; ao passo que as limitações dizem respeito a áreas com relevo forte ondulado a montanhoso, solos jovens (Neossolos Litólicos). O estudo foi relevante, pois permitiu conhecer de forma integrada a área do município de Juazeiro do Piauí, contribuindo para o planejamento e o uso sustentável dos mesmos no município.

In this study, a methodology for automatic recognition of multiple simultaneous types of partial discharges (PDs) in hydro-generator stator windings was proposed. All the seven PD sources typical in rotating machines were considered, and up to three simultaneous sources could be identified. The functionality of identifying samples with no valid PDs was also incorporated using a new technique. The data set was composed of phase-resolved partial discharge (PRPD) patterns obtained from on-line measurements of hydro-generators. From an input PRPD, noise and interference were removed with an improved version of an image-based denoising algorithm previously proposed by the authors. Then, a novel image-based algorithm that separates partially superposed PD clouds was proposed, by decomposing the input pattern into two sub-PRPDs containing discharges of different natures. From the sub-PRPDs, one extracts features quantifying the PD distribution over amplitudes and the contour of PD clouds. Those features are fed as inputs to several artificial neural networks (ANNs), each of which solves a part of the classification problem and acts as a block of a larger system. Once trained, ANNs work collaboratively to identify an unknown sample. Good results were obtained, with overall accuracies ranging from 88% to 94.8% for all the considered PD sources.

With the recent advancements in power electronics for wind turbines (WTs) and increasing penetration of wind energy, wind power plants (WPP) have become necessary contributors of reactive power support for the bulk power system. Balancing reactive power support with individual WT operating requirements in a cost-effective manner is a challenge for WPP designers. In this paper, we present a methodology to optimize the WPP reactive power capability as seen from the point of common coupling (PCC), accounting for steady-state operating capabilities of the WPP equipment. Thus, the proposed methodology determines the configuration of the tap-changing transformers within the WPP that maximizes the amount of reactive power the WPP can either consume or inject to the network, considering uncertain levels of wind power generation and voltage magnitudes at the PCC. The optimized reactive power capability (ORPC) problem is initially formulated as a mixed-integer nonlinear programming (MINLP) model. Then, a set of efficient linearization techniques are used to obtain a mixed-integer linear programming (MILP) model that can be solved via off-the-shelf mathematical programming solvers. Results demonstrate that the proposed MILP model is a scalable, flexible and accurate method to maximize the reactive power capability of WPP.

The black liquor is a byproduct of the kraft pulping process that contains more than half of the exergy content in the total woody biomass fed to the digester, representing a key supply of renewable energy to the pulping process. In this work, the conventional scenario of the black liquor use (i.e., concentration and combustion) is compared with the black liquor upgrading (via) gasification process for ammonia production in terms of economics, exergy efficiency and environmental impact. The combined energy integration and exergy analysis is used to identify the potential improvements that may remain hidden to the energy analysis alone, namely, the determination and mitigation of the process irreversibility. As a result, the exergy efficiencies of the conventional and the integrated cases average 40% and 42%, respectively, whereas the overall emission balance varies from 1.97 to −0.69 tCO2/tPulp, respectively. The negative CO2 emissions indicate the environmental benefits of the proposed integrated process compared to the conventional kraft pulp mill.

[EN] The service life of real construction elements is usually long, so the study of the behavior of cement-based materials with new pozzolanic additions in the very long term, after several hardening years, could be interesting. Here, the influence of using waste brick powder as 10% and 20% clinker substitution in microstructure and several durability-related parameters of mortars after 1500 hardening days (approximately 4 years) has been studied. According to the results obtained, the incorporation of brick powder overall improved the performance of mortars after 4 years, compared to reference mortars without addition, especially regarding the pore structure and chloride diffusion. This work was supported by the Conselleria de Educacion, Inves-tigacion, Cultura y Deporte (at present re-named as Conselleria de Innovacion, Universidades, Ciencia y Sociedad Digital) de la Generalitat Valenciana (Spain) [grant number GV/2019/070] ; and by the Agencia Nacional de Investigacion y Desarrollo de Chile (ANID) [grant number FONDECYT REGULAR 1211135]

Abstract Experimental analysis of viscosity can be a straightforward and inexpensive analysis for few samples. However, in industrial processes that have high demands of properties measurements, the determination of viscosity and other properties involves time-consuming with sampling, analysis and availability of results. Also in refineries, the sampling routines for experimental determination of the viscosity of streams are not enough to represent variations that occur in the process, such as the shift of an oil tank in distillation units. In addition, besides requiring cost of operating personnel and laboratory analyst, all of these steps can take up to one shift until the result is available. Therefore, as an alternative, the use of predictive methods of kinematic viscosity are essential. Empirical methods have been used in simulations and design calculations of streams and mixture at industries regarding kinematic viscosity (KV) of petroleum fractions and fuels at different temperatures. However, there are uncertainties about the most accurate method to use at specific condition (temperature, feedstock, volume fraction) which might affect the KV prediction of fuels with unknown composition. Therefore, we assembled and evaluated several methods to predict KV of different diesel systems. In addition, new methods for predicting KV of diesel fractions at several temperatures were also developed for improving the estimation accuracy. As a result, we developed a guide with suggestions of the most accurate models to be applied for diesel fraction from assays, diesel fractions S500 from blend system at several temperatures, and biodiesel-diesel blends at different temperatures, volume fractions and feedstock.